midi gradually out of sync

troven wrote on 4/26/2002, 7:30 PM

i know i've read similar posts before but i've just read through a dozen 'close' ones that didn't really answer my question - this may have happened to some of you too.

i'm doing my midi sequencing of drum tracks in cakewalk 9.03 - i exported a 16 bit 44.1k wav file of the song minus the click track from vegas to use as my guide. I've got the programming all done and cakewalk is sequencing my akai s6000 sampler and everything sounds great. now - i want to get this all out of midi and into vegas so i can mix. So, I set vegas to generate midi clock (using SF's virtual midi router) and set Cakewalk to chase to midi clock. no problems yet. I solo the kick channel on cakewalk and push play - where it says - 'waiting for midi clock'. then i go back to vegas and create a new audio channel, arm it for record and hit record - no problems. vegas triggers cakewalk and it looks like we're off and running. the problem is, that by the end of the 5 minute song - the kick is way behind the beat. it looks like it's been gradually lagging the whole time.

my sound card is an echo layla 24, my midi interface (aside from the virtual router) is an emagic amt-8.

so i'm not sure if this is a cakewalk question, a vegas question, a midi question or a hardware question. anyone else ever experience this?

--t

Comments

troven wrote on 4/27/2002, 12:46 AM

ok, another test - i saved the kick drum track only out of cakewalk as a midi file and brought it into acid - it still worked fine and triggered my akai sampler. then, i set acid to record the input (onto a 2nd acid track) on the soundcard at the same time it played back the midi file on track 1.

when this was done i played the midi file and the recorded wav file together and got increasing amount of flam from the beginning to the end. by the end of the track it was almost a beat behind. and this is all within the same program - so it's not an external sync problem.

yes i've got the latest drivers, my os is 98se - i've used vegas for a year with no problems but this is the first time i've ever recorded drums in this way (one long track) usually i create loops externally and add the parts into vegas so they never have time to drift.

ideas?

--t

pwppch wrote on 4/29/2002, 10:28 PM

Is the sync lost if you only playback and not record? (Do everything you are doing, but hit play vs record in Vegas.)

Peter

troven wrote on 5/1/2002, 11:45 PM

yes - there is no difference between play and record. i've even loaded the midi file onto the akai with a downbeat that corresponds to an exact point in the vegas track. i then just hit record in vegas and a second later hit play on the akai and capture the whole drum part. i then manually adjust the downbeat to the correct spot - and the same thing happens. it starts off in perfect sync and then drifts toward the end. this pretty much eliminates MIDI sync as a culprit.

i tried this recording the track to both 24/88.2 and 16/44.1 .wav files - same effect.

i eventually got around the problem by manually splitting the track every 4 bars and nudging it back to the grid markers. My PC has no trouble playing 15 or so tracks of 24/88.2 audio so i'm thinking this must be limited to a recording problem.

i've heard of this on several other occasions but the last bunch of threads that started out trying to trouble shoot - ended up devolving into a flame war - go figure.

anyway, thanks for reading (sonicPCH)

-t

pwppch wrote on 5/4/2002, 2:56 AM

It sounds like something is interpretting the tempo wrong. I am not familiar with the AKAI unit, but for it to drift out of time on its own is rather annoying - if I understand what you did.

Hmmm.

Peter

troven wrote on 5/5/2002, 11:32 PM

it's not the akai unit - akai's midi timing is pretty legendary. - vegas and the PC is what's getting out of sync. apparently PC's can't lock to a word clock so they do what's called 'free-wheel'. Still in a testing frame of mind, I recorded the metronome output of cakewalk 9.0 into vegas while locked to midi clock and the same drift occurred.

a friend at a post-pro house said this was a very common problem with prosumer type pc recording systems. The solution unfortunately is quite costly. although my soundcard has word clock I/O there's nothing on the PC's recording side that can lock to it. apparently the problem is alleviated somewhat with faster processors. looks like my Dell PIII600 gets about 30 seconds of decent free-wheel sync. a p4 2ghz will get more i suspect ;)

if i'm mistaken about any of this please chime in - i'm just assembling info from everywhere - in the meantime i'm not too bothered i just split and nudge! keeps me hands-on!

--t

RumpL4skn wrote on 5/6/2002, 4:16 PM

I don't if this helps, but I've had similar problems with Vegas and a Roland MC-80 stand-alone. Apparently the Roland's clock runs differently when in play and in record, as it never syncs the same in those 2 states. Even worse, the MC-80's clock runs at a different standard than a PC clock. I know some people will say this is bull, but I've proven it. The MC-80 has been discontinued since, and I don't doubt it was related to it's sync performance. Otherwise, as a stand-alone, the unit is fabulous.

pwppch wrote on 5/6/2002, 10:10 PM

Word clock is actually something that your sound card and external hardware should have in common. This type of connection assures that both are using the same exact sample rate.

This should not effect MIDI clock sync however. The slave - AKAI - should be following the MIDI clock to generate its internal tempo.

If your sound card has a Word clock output, then you should connect this to the AKAI's Word Clock input. If it is the other way around, the connect accordingly and tell your Sound card that it should use its word clock input as its clock source.

At the very least you will have the two units using the same sample rate.

Peter

Rednroll wrote on 5/7/2002, 7:53 PM

I do this type of stuff all the time. I have a similar setup. I have an Akai
S-2800. I'm not quite familar with the S-6000, but I'm assuming you're midi sequence from Cakewalk is only triggering your sampled drum sounds in the S-6000? Or does the S-6000 have an internal sequencer you're triggering also? My sequencer is on a seperate PC, so I'm not using the the 'Virtual Midi router'. In Vegas are you generating "Midi Time Code" or "Midi Clock" for Cakewalk to chase too? I usually generate "Midi Time Code" from Vegas and have my sequencer chase to that. If you are using "Midi Time Code" then make sure Vegas is generating 30 FPS, and then Cakewalk is chasing to "Midi Time Code" 30 FPS. You might have one set at 29.97 and the other at 30 fps, which would give you the drift you're experiencing. If this doesn't work, then try setting Vegas to generate "Midi Clock" and make sure Cakewalk is set up to receive "Midi Beat Clock".

Like I said though, I haven't had this problem having my sequencer and Vegas on seperate machines and sending midi time code through my MOTU midi interfaces on each PC, and having my sequencer chase to Vegas. I have run into a similar situation in a pro post house when syncing a hard disk editor set at 30 fps 44.1Khz, and syncing to Video tape decks which put out 29.97. It would stay in sync for short programs 30 seconds in length (ie TV commercials), but when we had jobs that where over 30 seconds we would have to change the hard disk editor to 29.97 FPS 48Khz, otherwise there would be a drift between the video and the audio. I believe there is some correlation between Frame rate and Word Clock (ie sample rate) in this manor when syncing to "Mide Time Code" (ie SMPTE). I'm not so certain on this though. Best practice taught me to use 29.97 FPS when recording at 48Khz and 30 FPS when recording at 44.1Khz....so if you're recording at 88.2Khz, this would go along with the 30 FPS selection.

Hope some of this might help you out.

BTW, You're "post pro" friend doesn't happen to be a MAC user does he? I've heard bogus statements like that from old MAC heads that I've worked with in the past in post houses. I can assure you, it is quite possible to get solid sync on PC's. I'm living proof of that using Windows 98 SE.

rednroll

troven wrote on 5/8/2002, 9:29 PM

thanks rednroll - your post was really well thought out and had a lot of helpful tips. in answer to your question the s6000 has a midi file 'player' but not a traditional sequencer. so basically it can't be triggered - but this was a last resort anyway. i checked all the things you pointed out and used MTC instead of midi clock and got the best results so far - it still drifts noticably by the halfway point (2 min) but i have to say i feel like it may be my hard drive (7200rpm 60 gig) that 'feels' like it's choking a bit. It's pretty full so not very optimized. this may or may not be it but i'll keep toying with this because i agree with you 100% that my 98se machine is amazing in every other respect (even though it's an aging pIII 600)

it's frustrating that i've never really seen evidence of mtc or midi clock really locking things together tempo wise - on my machine anyway.

thanks again.

--t

Rednroll wrote on 5/8/2002, 10:56 PM

You may be correct. What I would try next is defragging that hard drive, also make sure DMA is enabled. For 60gig, you better start defragging and let it run overnight. The thing you might want to try is recording at 44.1Khz instead of the 88.2Khz. 88.2Khz is requiring double the amount of speed your drive has to record data at. I feel 88.2Khz is way overkill and unnecessay. It would be a good test to layoff the same sequence at 44.1Khz and see if you experience the same drift problems. If this fixes the problem, then I would conclude you are correct in your assumption with your hard drive.

Also, do you have that entire 60gigs on 1 partition? I usually find it better to create a seperate partition to record your audio tracks on. It makes defragging a partition less painful, and also keeps your audio data in the same relative locations on the hard drive platters, instead of sticking it all over the place, which causes the heads to have to move faster to different locations on your hard drive. It's also a good idea to keep your OS on it's own seperate partition.

troven wrote on 5/9/2002, 9:18 AM

i'll try that rednroll - my 60 gig drive is actually drive D: and is audio-only. OS and programs are all on drive C: (i learned that lesson a while ago!) In the mean time, i created a new project in vegas set to 44.1/16 and 120 bpm and set to record on my C (non-audio) drive - then i created a 120bpm track of midi kick drums on the 1/4 notes in cakewalk that were to sequence the akai s6000 drum program - i set vegas to send out MTC and cakewalk to chase to MTC (via SF's virtual midi router) and turned on the metronome in vegas (the true test)

my first try was good but slightly shakey - which makes the hard drive problem seem very likely.. on my second try, for the hell of it - i set MTC output in vegas to 'use internal timer for MTC generation' - i had no idea what this means or why it would be better - but it was (maybe you could explain). the kick drum and metronome locked together for 3 solid minutes. finally!!

now i'm going to defrag and take your advice to record the drums at 44.1 not 88.2 and see what happens. thanks again for helping me troubleshoot this problem. it's been really confusing but i'm starting to see the light.

--t

Rednroll wrote on 5/9/2002, 10:07 AM

I believe when you set in to "internal timer" it will use your PC's internal clock to use as the clock reference. When you set it to "external timer" it will use whatever your sound card is using for a word clock. My sound card has a external/internal clock setting, which I switch depending on if I'm recording digital audio (external clock), or playing back digital audio to an external device (internal setting). When you set Vegas to use the "external timer", it will use whatever clock your sound card is using. Which may be "internal" anyways if your clock is set to "internal" on your sound card. I usually leave this setting on "external timer", therefore it switches depending on if I'm playing back or recording digital audio, and changes with the internal/external clock if I switch this on my sound card. This will only work properly if you understand how to transfer digital audio to and from external hardware properly. You may have had Vegas set to "external" and then your sound card was set to "external", but weren't feeding your sound card with an "external" word clock, or your sound card was receiving external 48Khz word clock, while trying to record in Vegas at 88.2khz. If this was the case and there was no external word clock being fed to your sound card, then vegas didn't have a good clock reference to do all your MTC (smpte) sync.